This disclosure generally relates to light sensor devices for use in marking methods and systems.
This disclosure refers to “marking” as a process of producing a pattern, such as text and/or images, on substrates, such as paper or transparent plastic. A marking engine may perform the actual marking by depositing ink, toner, dye, or any other suitable marking material on the substrate. For brevity, the word “toner” will be used to represent the full range of marking materials, and is used interchangeably with the terms for other identifying materials in the full range of marking materials.
A popular marking engine is the xerographic marking engine used in many digital copiers and printers. In such a xerographic marking engine, a photoreceptor unit, such as, for example, a belt or roller, whose electrostatic charge varies in response to being exposed to light, is placed between a toner supply and the substrate. In systems including xerographic marking engines, the toner is typically an electrostatically chargeable or electrostatically attractable toner. A laser unit, bank of light emitting diodes, or other such light source, is used to expose the photoreceptor unit to light to form an image of a pattern to be printed on the photoreceptor unit. In simple, monochromatic xerographic marking engines, single color toner is electrostatically attracted to the image on the photoreceptor unit to create a toner image on the photoreceptor unit. The toner image is then transferred to the substrate from the photoreceptor unit. Different methodologies are then employed to heat-set or otherwise “fuse” the toner image onto the substrate.
In more complex systems, multiple colors of toner are applied. General categories of more complex color systems include those that are referred to as Image On Image (IOI) systems and/or tandem systems. In an IOI system, such as that shown schematically in exemplary manner in FIG. 1, the marking engine 10 includes a plurality of primary color applying units 11 that deposit toner on a photoreceptor belt 13, which includes multiple image forming areas 14, hereafter pitches 14. A first pitch 14 of the photoreceptor belt 13 receives a first toner image in a first color. The first color remains on the photoreceptor belt 13 while second (and subsequent) toner images are created by applying second (and subsequent) colors atop the first image in the same pitch 14. The first and second (and subsequent) toner images remain on the photoreceptor belt 13 and are subsequently built up on the photoreceptor belt 13. Once all of the toner images are placed on the photoreceptor belt 13, they are then transferred to a substrate, typically paper, and fused to the substrate. Furthermore, after the first pitch 14 has passed one of the color applying units 11, the next pitch 14 comes into alignment with that color applying unit 11, and the image forming process starts again in the next pitch 14.
In an embodiment of a tandem system architecture, such as that shown in exemplary manner in FIG. 2, the marking engine 20 includes multiple primary color applying units 21 that first deposit their toner on respective photoreceptor drums 22 to form toner images. These toner images are deposited on an intermediate transfer belt (ITB) 23, which includes multiple pitches 24. Each toner image is transferred onto the ITB 23 before the next toner image is formed. Like in the IOI system, the toner images are transferred to a substrate once all toner images for a given pitch have been deposited on the ITB 23.
In a variant of the tandem system shown in FIG. 2, an additional drum may be included between each photoreceptor drum 22 and the ITB 23. The additional drum accepts the toner image from the photoreceptor drum 22 and deposits it on the ITB 23. The inclusion of the additional drum aids in reducing a possibility of toner contamination by toner of one color getting into a toner source of another color due to electrostatic interaction between the toner image on the ITB 23 and the photoreceptor drum 22.